Molecular beam epitaxy growth and characterization of beryllium-based II-VI semiconductor materials and distributed Bragg reflectors for potential application in visible light emitters.
Item
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Title
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Molecular beam epitaxy growth and characterization of beryllium-based II-VI semiconductor materials and distributed Bragg reflectors for potential application in visible light emitters.
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Identifier
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AAI3037418
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identifier
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3037418
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Creator
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Maksimov, Oleg.
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Contributor
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Adviser: Maria Tamargo
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Date
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2002
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Inorganic | Physics, Condensed Matter | Engineering, Materials Science
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Abstract
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This thesis describes the molecular beam epitaxy (MBE) growth and characterization of ZnxCdyMg1-x-ySe-based distributed Bragg reflectors (DBRs) and new BexZnyCd1-x-y Se and BexZn1-xTe material systems on InP substrates. DBRs can be integrated with ZnxCdyMg 1-x-ySe-based light emitting diodes (LEDs) to fabricate resonant cavity LEDs (RCLEDs) that have better spectral purity and higher emission intensity than the conventional LEDs. The BexZny Cd1-x-ySe alloy can be used as an active layer and the BexZn1-xTe alloy can be used as a p-type contact layer in ZnxCdyMg1-x-ySe-based LEDs. Application of these materials is proposed to improve reliability as well as the optical and electrical properties of light emitters.;DBRs with different numbers of periods and different layer composition were grown by MBE from ZnxCdyMg1-x-y Se-based materials on InP substrates. Their reflectivity maxima were controlled by the individual thicknesses of constituent layers, and were adjusted in the range of 615--500 nm, covering the red, green, and blue-green regions of the visible spectrum. A maximum reflectivity of 95.5% was obtained for a DBR with 16 periods. Electrical properties of chlorine-doped n-type ZnCdSe/ZnCdMgSe DBR structures were also investigated and high carrier concentration was achieved in the constituent layers. These results demonstrate that Zn xCdyMg1-x-ySe is a promising material system for the design of highly reflective, conductive DBRs for application in high efficiency RCLEDs.;BexZnyCd1-x-ySe epilayers and Be0.08Cd0.92Se/Zn0.32Cd0.25Mg 0.43Se quantum well (QW) structures were grown and investigated. Their high crystalline quality was established using X-ray diffraction measurements. Efficient excitonic emission was observed both from the BexZn yCd1-x-ySe epilayers and the QWs. Based on these results and on the expected lattice hardening properties of BeSe, we propose that BexZnyCd1-x-ySe is an attractive QW material for light emitters.;The growth and optical properties of a set of BexZn1-x Te epilayers were studied. Comparison of the reflectivity and the photoluminescence spectra allowed us to locate the direct-to-indirect band gap crossover for this alloy at x ≈ 0.28. Our results indicated that Be0.48Zn 0.52Te, which is the composition that is lattice matched to InP, is an indirect semiconductor with a Gamma → X indirect band gap of 2.77 eV, and a Gamma → Gamma direct band gap of 3.14 eV. Therefore, it is transparent for the visible light and can be used as a top p-type contact layer in LEDs.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
